The present invention relates generally to liquid processing machinery and, more specifically, to filters designed to remove debris from backwashed liquid while returning the backwashed liquid to the normal forward liquid filtering process.
For the purpose of clarity, swimming pools will be used to exemplify the problems associated with this mode of filtering, although many industrial and residential liquid filtering applications present similar problems and may be solved by use of an embodiment of the instant invention.
Swimming pools water contains a great deal of debris suspended in solution including leaves, soil and insects. A number of filtering systems are available which filter this material which tends to gather at the top surface of the water due to water tension. Water flows into a skimmer, is pumped through a filter medium, either sand or diatomaceous earth and is then returned to the pool. Debris is trapped on the surface of the filter medium and unless removed clogs the filter, reducing the flow of water and possibly causing damage to the pump. Micro organisms may also flourish under these conditions.
The common remedy to this buildup of debris is to periodically reverse the water flow through the filter medium thereby dislodging the debris. This process is referred to as "backwashing" and is usually accomplished by using a backwash flow valve associated with the filter. Most filter manufacturers supply this valve as part of a filter package.
The debris-containing backwashed water is normally conducted through a long hose and is discharged into the earth or to a sump located as far as possible from the pool. The cost of water is rising almost everywhere due to increasing demand and decreasing pollution free supplies. This backwashed water, therefore, represents a significant waste of economic and natural resources. Also discharging polluted debris filled water into the earth is unsightly, unhealthy and illegal in some localities.
A number of inventions have addressed the issue of pool filtering in general. For example, C. Whitmer (U.S. Pat. No. 3,969,248), M. Baker (U.S. Pat. No. 4,194,975) and V. Kelly (U.S. Pat. No. 4,115,276) addressed general pool filtering systems, a backwash system for swimming pools and a multi-port backwash valve respectively, but, none of these inventions relates in any way whatsoever with the problem of discharged backwashed water.